1. Field of the Invention
This invention relates to the field of sound simulators, and particularly to sound simulators for the generation of engine sounds with load effects.
2. Description of the Related Art
Modern-day virtual reality simulators, such as video and computer games, often require realistic vehicle engine sounds to accompany the action being displayed. Various techniques have been used to provide such sounds.
One method used to simulate vehicle engine sounds relies on the playback of looped sound waves, where the pitch of the waves varies according to the simulated RPM or speed of the vehicle.
This approach neglects several important aspects that are found in the engine sounds of actual vehicles. For example, such looped sample-based solutions lack variation according to load. Most vehicles have an engine that must perform more work when accelerating, which alters the texture of the engine sound. Recordings taken of steady-state vehicle sounds are unable to capture the variations in load that are associated with acceleration and deceleration.
Another problem with prior art efforts is the unnatural shifting of formants. Formants are a characteristic set of peaks in the frequency response of an object's sound, associated with resonances within the physical system. For most vehicles, there is a fixed set of formants that is independent of the speed of the vehicle or the RPM of the engine. When a sound sample is taken of a vehicle, the formants in the sample are only accurate when the sample is played back at the pitch at which it was recorded. As prior art methods of vehicle sound simulation pitch the sample up and down, the result is a sound that has formants which shift up and down, resulting in an unnatural sound.